1. Field of the Invention
The invention concerns a method for the manufacture of a superconductor with a layer of the A-15 phase of the system Nb-Al-Si.
2. Description of the Prior Art
The A-15 phase of the system Nb-Al-Si, which has a composition of approximately Nb.sub.3 (Al.sub.1-x Si.sub.x) with 0&lt;x&lt;0.3, becomes superconducting at relatively high temperatures and changes from this state only in very strong magnetic fields. In a single-phase sample of the composition Nb.sub.75.3 Al.sub.21.5 Si.sub.3.2 which was obtained by melting the elements, for instance, a critical (transition) temperature of 19.2.degree. K was measured (see Zeitschrift fuer Naturforschung 26b, (1971), pages 1035 to 1039). The A-15 phase mentioned is therefore of great technical interest, for instance, for use in superconducting magnet coils. However, the technical application of this A-15 phase has so far been unsuccessful because no simple and economical method for manufacturing, in particular, wire-or ribbon-shaped conductors with a layer of this A-15 phase is known. A conductor with a layer of the A-15 phase is desirable, however, because the A-15 phase is very brittle and can be deformed elastically only to slight degree. In technically usable superconductors, the A-15 layer must therefore be only a few .mu.m thick and should be situated as closely as possible to the neutral fiber of the conductor.
It is an object of the invention to make possible, as simple as possible, the manufacture of superconductors with a layer of the A-15 phase of the system Nb-Al-Si, while at the same time achieving the highest possible transition temperatures and critical current densities usable for technical applications. In particular, continuous manufacture of long wires or ribbons with thin layers of the A-15 phase mentioned should be possible.